The present invention relates to electrical connection assemblies.
Hard disc drives (HDDs) typically comprise one or more data storage discs, each disc having concentric data tracks for storing data. Where multiple discs are used, a stack is formed of co-axial discs having generally the same diameter. A transducing head carried by a slider is used to read from and write to data tracks on an associated disc. The slider is carried by a head arm assembly (HAA) that includes an actuator arm and a suspension, and can include a separate gimbal structure or can integrally form a gimbal with the suspension. As the disc is spun, the slider glides above the surface of the disc on a small cushion of air. The actuator arm movably positions the slider with respect to the disc. Electrical connections extend along the suspension to electrically connect the transducing head to components located at or near the actuator arm. Those electrical connections can be formed on the suspension itself, or can be located on a separate electrical interconnect structure supported relative to the suspension, such as a flex-on suspension (FOS).
A typical slider includes a slider body (often called the “substrate”) and an electrically insulative overcoat that supports a transducing head. In some configurations, a plurality of bond pads, usually a minimum of four, are formed at a side or edge of the slider—typically at its trailing edge. In alternative configurations, “top” bond pads are located on a back side of the slider (synonymously called the “top” of the slider). In either type of configuration, the bond pads are electrically connected through the overcoat to various components, such as to the transducing head or to a heater.
During fabrication of a HDD, the slider is mechanically secured to a load button or load point of the gimbal at the top (or back side) of the slider, for example, with an adhesive. Next, the bond pads are electrically connected to the electrical connections (i.e., traces) along the suspension. Conventional gold ball bonding, solder reflow, friction welding and solder jetting operations are used to make the electrical connections from the bond pads of the slider to connection points for the traces along the suspension.
In some situations, it is desirable to provide large numbers of electrical connections to a slider. The sizes of sliders and transducing heads continue to decrease, and trends are for sliders to continue to be smaller. Also, the sizes of bond pads generally decrease with smaller slider sizes. However, relatively small slider and bond pad sizes present numerous difficulties for providing relatively large numbers of electrical connections (e.g., bond pads) to a slider in a relatively small space. Relatively small, closely-spaced bond pads tend to present undesirably high manufacturing yield losses. For example, conventional soldering methods and equipment can present risk of bridging adjacent bond pads, which essentially results in undesired shorting between those bond pads as solder material adheres to multiple bond pads. Solder reflow methods require heating of the entire article on which bond pads are located, which presents a risk of damaging sensitive structures, such as transducers carried within a slider that is heated. Friction welding methods can require an undesirably large space for clamping parts to be welded, and can place design-restrictive rigidity requirements on those parts. Furthermore, slider designs using top bond pads can be undesirably costly, for instance, in terms of time and equipment required for fabrication.